Safety device for preventing the return movement of electrodes in electric furnaces or similar apparatuses

ABSTRACT

Safety device for preventing the return movement of electrodes in electric furnaces and similar furnaces or plasma burners. The safety device comprises a sleeve and a holder. The safety device comprises a sleeve and a holder. The holder is secured to the upper part of a furnace and the sleeve, supported by the holder, concentrically encircles the individual electrodes. The sleeve is formed with bores which receive electrode-clamping elements which clampingly cooperate with the electrode and the holder.

[ 1 May 30, 1972 [54] SAFETY DEVICE FOR PREVENTING References Cited THE RETURN MOVEMENT 0F ELECTRODES IN ELECTRIC FURNACES OR SIMILAR APPARATUSES UNITED STATES PATENTS Wooding............................... 7/1962 r mm mm m m. N M l 7 m .ni mm 0 mx m m mm mp f O mm m mm B H m e mm m m mum m mm "mm HSG m m n e V m n n [73] Assignee:

'Knapsack Aktlengesellschaft, Knapsack Atwmey Cnny and Hutz near Cologne. Germany Jan. 4, 1971 ABSTRACT [22] Filed:

Safety device for preventing the return movement of electrodes in electric furnaces and similar furnaces or plasma bur- [21] 7 .Appl. No.:

ners. The safety device comprises a sleeve and a holder. The

{30] Foreign Application Prior), Data safety device comprises a sleeve and a holder. The holder is Jan. 9, 1970 secured to the upper part of a furnace and the sleeve, supported by the holder, concentrically encircles the individual electrodes. The sleeve is formed with bores which receive Germany.....................

v13/15 electrode-clamping elements which clampingly cooperate [51] Int. 7/12 withtheelectrode andthe l [58] Field oiSearch..................13/l4, 15, 16; 314/103; 112,

314/88, 101 9 Claims, 3 Drawing Figures w my 1.1/1 a; :52 7 3 I SAFETY DEVICE FOR PREVENTING THE RETURN MOVEMENT OF ELECTRODES IN ELECTRIC FURNACES OR SIMILAR APPARATUSES The present invention relates to a safety device for preventing the return movement of electrodes in electric furnaces or similar apparatuses including, for example, plasmabumers, such as. those used for cracking hydrocarbons to give acetylene, ethylene, methane and hydrogen.

It is known to advance or lower self-consuming electrodes in electric furnaces or plasma burners during operation, consistently with the electrode consumption, by means of electrode feeders. In association with this operation it is possible to monitor these apparatuses with respect to the relation existing between current, voltage and resistance.

The above-mentioned electrode feeders essentially comprise conveyor or friction rollers, of which the shape is made to conform to that of the electrode used in a given case. The rollers, which are caused to rotate at a controlled speed, are pressed against the electrode and impart feed motion to it. A critical factor with regard to the power transferable to, and necessary for the forward movement of, the electrodes is the friction which occurs between the electrodes and the rollers.

Certain other known feeders for advancing electrodes are fitted with hydraulically actuated gripping jaws, or with thin plate-like or lamellar holders. Once again, the friction between the feeder and the electrodes is critical for the feed power transmitted to the electrodes.

Still further known electrode feeders have conveyor or feeding means which support and clampingly receive the electrodes, and gear drives, rack-and-pinion drives, or worm gears or worm drives, are used to impart a feed motion to the electrodes.

Electrode feeders fitted with conveyor roller drives similar to friction rollers, hydraulically operated feeders fitted with clamping jaws, and the various gear feeders having no selflocking gears, are not, however, fully satisfactory. The reason for this is that the sudden generation of overpressure in the interior of an electric furnace, especially in the interior of a closed burner system, may produce return movement of the electrodes, since the over-pressure may be sufficient to overcome the frictional forces between the electrodes and conveyor means and to move the electrodes away from the burner in a direction opposite to the electrode feed motion. Minor displacement of the electrode produces adverse effects upon the current-voltage ratio. In the case of more serious displacement, however, the electrode may even be ejected from the furnace and destroy the burner system.

It is an object of the present invention to provide a satisfactory device of the type first described hereinabove which enables electrodes to be reliably advanced and, at the same time, return movement thereof to be effectively avoided. This is achieved in accordance with the present invention by associating with each electrode a sleeve which concentrically encircles the electrode and is supported, with resilience in the axial direction, by a holder held on to the upper part of a furnace, the sleeve being formed with bores which are uniformly distributed around it and receive electrode-clamping elements that clampingly cooperate with the electrode and the holder.

This arrangement provides a fully satisfactory safety device for preventing the return movement of electrodes, more particularly the ejection of electrodes from a furnace. It should be added that the present safety device for preventing the return movement of electrodes works independently of the electrode feeder system, and can conform automatically to radial centering movements of the electrode and an irregular electrode surface, if any.

Preferred features of the present invention provide:

a. for the sleeve to bear resiliently against the holder by means of springs;

b. for the use of balls as clamping elements and for the internal surface of the holder to be conically tapered upwardly;

c. for the use of rollers or tilting levers as clamping elements and for the internal surface of the holder to be formed with grooves as an abutment for the rollers or tilting levers;

. of the furnace; and/or e. for the use of retaining rings, retaining lugs or other retaining means to hold the holder on to the upper part of the furnace so as to be radially displaceable thereon.

An exemplary embodiment of the present invention is illustrated in the accompanying drawing. Needless to say, the invention is not limited thereto and admits of various modifications without departing from its scope.

In the accompanying drawing:

FIG. 1 is a side-elevational view of the upper part of a furnace;

FIG. 2 is a cross-sectional view taken along line ll II, and

FIG. 3 illustrates a modified embodiment of the present invention.

The safety device illustrated in the accompanying drawing and designed in accordance with the present invention is used to prevent the retummovement of electrodes in electric furnaces or similar apparatus, for example plasma burners, such as those used for cracking hydrocarbons to give acetylene, ethylene, methane and hydrogen. As can be seen, the individual electrodes of which one is shown at 1 are each concentrically surrounded by a sleeve 4 which bears axially, with resilience, against a holder 8 by means of springs 10. Holder 8 is fast with the upper part of furnace 3. Sleeve 4 has bores 5 which are distributed around it, at 45 intervals in the case illustrated, and which receive balls 6 (FIGS. 1-2) or tilting levers 14 (FIG. 3), as clamping elements. The inside surface 9 of holder 8 is conically tapered upwardly if use is made of balls 6, or is formed with grooves 15 (as an abutment) if use is made of tilting levers 14.

Holder 8 may be rigidly secured to the upper part of furnace 3 by means of bolts 1 l, as shown on the right-hand side of FIG. 1, or secured thereto so as to be radially displaceable thereon, by means of a retaining ring 12, as shown on the left-hand side of FIG. 1.

The safety device of the present invention is operated in the following manner.

By means of feed rollers 2, electrode 1 is conveyed through the upper part of furnace 3, being advanced through sleeve 4 in the direction of arrow a. The cylindrical portion of sleeve 4 is formed with bores or recessed annular apertures 5 receiving (in the embodiment of FIGS. 1-2) the balls 6, of which there should be at least three, eight balls 6 being used in the case illustrated. By means of a bolt-secured covering collar 7, balls 6 are held in position as in a ball-bearing cage, although they are radially displaceable in the directions indicated by arrows b and 0. Compression springs 10 which bear against holder frame 8 exert pressure against sleeve 4 in the direction of arrow d and force balls 6 into contact with the slightly conical inside surface 9 of holder 8. Sleeve 4 ceases to move away from holder 8 in the direction of arrow d as soon as the slight pressure exerted by springs 10 forces balls 6 into contact firstly with the conical inside surface 9 of holder 8 and secondly with electrode 1.

As mentioned earlier, the holder 8 may be fastened to the upper part 3 of the furnace by means of bolts 11, or may be loosely held by retaining ring 12, which is fast with part 3; in this latter case it is so held as to be radially displaceable in all directions and to follow centering movements of the electrode, if any, through angle 0:.

Once feed rollers 2 commence conveying electrode 1 in the direction of arrow a, the electrode has to overcome the slight contact pressure exerted by (in the embodiment of FIGS. 1-2) balls 6, and the electrode then rolls or slides down over balls 6. If, as a result of superficial uneveness of electrode 1, the sliding resistance between balls 6 and electrode 1 becomes excessively high, then balls 6 and sleeve 4 are conveyed in the direction of arrow a against the pressure exerted by springs 10 until balls 6, which are in contact with the conical inside surface 9 of holder 8, have sufficient room to move in the direction of arrow 0 and make way for the uneveness 13.

As soon as electrode 1 begins to move back in the direction of arrow e opposite to the direction indicated by arrow a, balls 6 are wedged between the conical inside surface 9 of holder 8 and electrode 1 in the direction of arrows c and b. The return movement of electrode 1 in the direction indicated by arrow 2 is resisted and in fact terminated, when the wedging effect firstly between electrode 1 and balls 6, and secondly between balls 6 and the conical inside surface 9 of holder 8, is strong enough to withstand the force urging the electrode 1 in the direction of arrow e. In the event that graphite or carbon electrodes are used, the balls may be found to penetrate into the relatively soft electrode material.

The same efi'ect can be produced by the substitution of tilting levers 14 (cf. FIG. 3), which bear against holder 8, for balls 6. The wedging effect is automatically loosened when the normal feed motion of the electrode in the direction of arrow a is resumed.

We claim:

1. A clamping device preventing the return movement of an electrode in an electric furnace, particularly in a plasma burner for cracking hydrocarbons, comprising a holder secured to the upper part of the fumace,a sleeve loosely concentrically disposed within the holder and encircling the electrode, the sleeve having bores uniformly distributed around it to receive electrode-clamping elements, resilient elements reacting between the holder and the sleeve in a direction parallel to the length of the electrode for supporting the sleeve about the electrode within the holder, clamping elements disposed in the bores of the sleeve and reacting clampingly between the electrode and the holder and having lines of action inclined toward the direction of movement of the electrode into the electric furnace for permitting the electrode to be advanced into the furnaces through the holder and sleeve and inhibiting any return movement thereof.

'2. The clamping device as claimed in claim I, wherein the resilient elements are compression springs and the sleeve bears resiliently against the holder by means of compression springs.

3. The clamping device as claimed in claim 1, wherein the clamping elements are balls and the holder has an inside surface which converges upwardly conically for reacting downwardly and inwardly against the balls.

4. The clamping device as claimed in claim 1, wherein the clamping elements are rollers and the inside surface of the holder is formed with recessed grooves as an abutment for the rollers and the recessed grooves having inside surfaces which converge upwardly conically for reacting downwardly and inwardly against the rollers.

5. The clamping device as claimed in claim 1, wherein the clamping elements are tilting levers and the inside surface of the holder is formed with recessed grooves as an abutment for tilting levers, and the tilting lever and recessed grooves being inclined toward the advancing direction of movement of the electrodes.

6. The clamping device as claimed in claim 1, wherein the holder is detachably secured to the upper part of the furnace.

7. The clamping device as claimed in claim 1, wherein the holder is secured to the upper part of the furnace and is laterally displaceable thereon.

8. The clamping device as claimed in claim 7, wherein the holder is held on to the upper part of the furnace by means of a retaining ring.

9. The clamping device as claimed in claim 7, wherein the holder is held on to the upper part of the furnace by means of retaining lugs. 

1. A clamping device preventing the return movement of an electrode in an electric furnace, particularly in a plasma burner for cracking hydrocarbons, comprising a holder secured to the upper part of the furnace, a sleeve loosely concentrically disposed within the holder and encircling the electrode, the sleeve having bores uniformly distributed around it to receive electrode-clamping elements, resilient elements reacting between the holder and the sleeve in a direction parallel to the length of the electrode for supporting the sleeve about the electrode within the holder, clamping elements disposed in the bores of the sleeve and reacting clampingly between the electrode and the holder and having lines of action inclined toward the direction of movement of the electrode into the electric furnace for permitting the electrode to be advanced into the furnaces through the holder and sleeve and inhibiting any return movement thereof.
 2. The clamping device as claimed in claim 1, wherein the resilient elements are compression springs and the sleeve bears resiliently against the holder by means of compression springs.
 3. The clamping device as claimed in claim 1, wherein the clamping elements are balls and the holder has an inside surface which converges upwardly conically for reacting downwardly and inwardly against the balls.
 4. The clamping device as claimed in claim 1, wherein the clamping elements are rollers and the inside surface of the holder is formed with recessed grooves as an abutment for the rollers and the recessed groovEs having inside surfaces which converge upwardly conically for reacting downwardly and inwardly against the rollers.
 5. The clamping device as claimed in claim 1, wherein the clamping elements are tilting levers and the inside surface of the holder is formed with recessed grooves as an abutment for tilting levers, and the tilting lever and recessed grooves being inclined toward the advancing direction of movement of the electrodes.
 6. The clamping device as claimed in claim 1, wherein the holder is detachably secured to the upper part of the furnace.
 7. The clamping device as claimed in claim 1, wherein the holder is secured to the upper part of the furnace and is laterally displaceable thereon.
 8. The clamping device as claimed in claim 7, wherein the holder is held on to the upper part of the furnace by means of a retaining ring.
 9. The clamping device as claimed in claim 7, wherein the holder is held on to the upper part of the furnace by means of retaining lugs. 